The present invention relater generally to data storage systems and more particularly, but not by limitation, to testing writer coils in data heads of a data storage system.
Data storage systems often utilize a data head having an inductive write transducer to store data on a surface of a recording media such as a disc. For example, in magnetic disc drive data storage systems, the data head associated with each disc surface will frequently include a magnetoresistive (MR) or a giant magnetoresistive (GMR) transducer (read head or reader) which reads magnetically stored data from the disc and a write transducer (write head r writer) which is used to write data to the disc. The write transducer of this type of data head typically includes a metallic coil through which current is passed to generate the magnetic fields necessary to write data to a surface of the disc.
In the writer coil of a data head, the coil inductance is linearly proportional to the number of turns in the coil, and is dependent upon the materials used and the conducting current. A coil with an open circuit (electrical discontinuity) wilt have zero admittance, while a completely electrically shorted coil will have infinite admittance. An insufficient number of turns in the coil can result in write failures due to weaker than necessary magnetic fields.
Lower than desired inductance values for the writer coil are typically caused by insufficient numbers of coil turns, having a partial short circuit in portions of the coil, or by other manufacturing faults. Infinite impedance is the other common symptom in writer faults, when the metallic coil becomes discontinuous and does not generate magnetic flux. Contemporary application specific integrated circuit (ASIC) technology has been used to produce numerous integrated circuit (IC) configurations which are capable of detecting writer coil open circuits (discontinuities), because of the simplicity required to detect this type of defect. However, it is far more difficult to detect short circuit defects in the writer coil. Since it is very desirable to filter out undesired writer conditions in head gimbal assemblies (HGAs) before being built into the finalized disc drive, an apparatus and associated method of detecting both electrical short circuits and discontinuities in the writer coil would be a significant improvement in the art.
Embodiments of the present invention relate to data storage systems which utilize a data head having a writer coil, and to apparatus and associated methods of identifying electrical faults in the writer coil.
In accordance with one embodiment of the present invention, an apparatus and associated method of testing a writer coil in a data head of a data storage system includes the steps of coupling detection circuitry to the writer coil and driving the writer coil with a periodic pulse signal generated by the detection circuitry. Next, a voltage is generated, with the detection circuitry, as a function of an inductance of the writer coil. Then, an inductance of the writer coil is calculated as a function of the generated voltage. Electrical short circuits and discontinuities in the writer coil are then identified as a function of the calculated inductance. An inductance detection circuit and a disc drive incorporating the circuit and the method are also disclosed.
These and various other features as well as advantages which characterize embodiments of the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.